1. Technical Field
The present application relates generally to apparatus and methods for automated inspection in semiconductor manufacturing and the like.
2. Description of the Background Art
Semiconductor wafer inspection apparatus typically image the wafer surface by either one of two techniques. A first technique involves scanning a square area of a stationary wafer. After that area is scanned, the wafer is moved over by the width of that square to acquire the next image. A second technique involves continuously scanning the wafer surface while, at the same time, moving the stage on which the wafer is mounted.
The wafer surface often has repeating patterns. In order to detect defects, the following method may be used. Image sections of repeating patterns on the wafer surface, displaced by one or multiple cell widths in the direction of the stage movement, are subtracted from each other to form a difference image. Such a difference image may be used as the basis for the defect detection.